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REVIEW 

-OF- 

ORE DEPOSITS 

-i N- 



I^LIDOLF KECK. 

• I 

COLORADO SPRINGS, COLO. 




DENVER: 

CHAIN & HARDY CO. 
1892. 








M'l' 


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> 




COPYRIGHT 1892. 

BY RUDOLF KECK 
ALL RIGHTS RESERVED. 



Vc> 



TO thh; honorable judges of the courts and the 

ATTORNEYS AT THE BAR OF THE COURTS OF THE STATE OF 
COLORADO, WHO HAVE BY THEIR OWN GOOD EXAMPLES 
GIVEN SUCH AN IMPETUS TO THP) STUDY OF THE ORE DE¬ 
POSITS OF OUR STATE, 

MOST RESPECTFULLY DEDICATED 

BY THE AUTHOR. 






REVIEW OF ORE DEPOSITS 

IN VARIOUS COUNTRIES. 


By RUDOLF KECK, Colorado Springs, Colorado. 


This review is written for readers who take an interest in 
mining affairs and wish to become acquainted with the geological 
relations of diverse mining districts. Its aim is to reach those 
who wish to form opinions on questions about ore deposits. 

If we could acquire a clear understanding of the genesis of 
ore deposits, we would be enabled to conduct the prospecting part 
of our mining business in a nlore rational manner. 

Realizing in our minds how small is that portion of the earth 
which is accessable to observation; smaller than the one six thou- 
santh part of the radius of our globe; we cannot trace the ele¬ 
ments of our ores back to that time when they were in a gaseous 
state. We must be satisfied to trace them to a period when they 
had entered into combinations which were left either naturally 
concentrated or finely distributed as silicates or as sulphides in the 
crystalline rocks, from which they can be transplanted to higher 
geological horizons by the chemical activity of percolating waters. 

Wherever two different rocks are in contact, access of water 
is facilitated, “All subterranean movements that produce joints 
and fractures in rocks, and the chemical action of the water cir¬ 
culating in the crust of our earth, have given origin and peculiari¬ 
ties to ore deposits.” (Dana-Geology.) 

In some cases it is evident that the origin of an ore deposit 
commenced with a more or less empty fissure caused by subter¬ 
ranean movements; but in many other cases, the veins have at¬ 
tained their present dimensions by the gradual solution, removal, 
and replacement of the rocks. 

There is no mineral in ore deposits which could not have ori¬ 
ginated out of aqueous solutions; the existence of some ore depos- 




2 


its of banded structure; the occurrence of minerals together with 
fragments of the wall-rocks in veins, a part of the fragments ap¬ 
pears to have been desintegrated by the action of water and pres¬ 
sure; the manner of dispersion of the ores through the deposits; 
the fact that there is no relation between the quantity of ore and 
the thickness of the vein; the constant circulation of waters above 
and in our earth; the absence of all indications of former intense 
heat within the ore deposits; the pseudomorphoses and paragenesis 
of minerals; the contemporaneous occurrence of refactory and un¬ 
refactory minerals, all these circumstances indicate that water was 
and still is the main agent in the formation of ore deposits in ^ the 
condition in which we find them to-day. 

Professor Sandberger at the University in Wuerzburg, Bava¬ 
ria, presuming that substances which occur together in such close 
connection as vein-material and ores must logically have a similar 
origin, took the pains to isolate the constituent silicates contained 
in eruptive rocks and in such belonging to the Archaean era, and 
to analyze them in larger quantities than generally used; for in¬ 
stance, the micas and hornblende. His results were astonishing. 
They demonstrate to irrefragable evidence, that not only the ele¬ 
ments of the gangue, but also the elements of the ores are con¬ 
tained in the crystalline rocks crossed by those ore veins, and that 
these metallic contents are found in the silicates of crystalline 
rocks of all geological periods and in their derivatives. He easily 
explains the chemical procedures, especially consisting in the re¬ 
duction of sulphates to sulphides by carbonaceous matter. In 
order to start these series of reaction it takes only solutions of 
alkaline carbonates or carbonic acid in water, percolating through 
the rocks; thereby the silicates are decomposed. The sulphates of 
alkalies being reduced to sulphides by carbonaceous matter change 
the compounds of the metals to the metallic sulphides. The pres¬ 
ence of sulphates in the crystalline rocks, Professor Sandberger 
explains, is found in the abundance of those microscopic cavities 
filled with alkali-salts and carbonic acid, the abundance of which 
is most remarkable. “It has been estimated that in some instances 
the number of these minute cavities in the crystals of rocks 
amounts to from one thousand millions to ten thousand millions 
in a cubic inch of space.” (Judd-Volcanoes.) 

Also the abundance of carbonacous matter in the earth is 
great; it not only penetrates with the meteoric water, but is also 


8 


present in the interior of the earth, arising either as gas or in 
mineral springs, or in being stored up either as petrified organic 
bodies in sedimentary rocks, or in the form of graphite, anthracite, 
asphalt and petroleum, or as the coloring ingredient of fluorspar, 
amethyst and smoky quartz; or in the minute cavities of the cry¬ 
stals enclosed in crystalline rocks; or disseminated through the 
extensive sediments of certain slates, dolomites, sandstones and 
conglomerates adjoining so many ore-deposits; not to speak of the 
sea so rich in organic substances. It is astonishing in how many 
ore-deposits we find carbonaceous matter still occuring. Petroleum 
for instance occurs in the copper-slate-beds of Germany; in the 
antimony mines in Westfalia; in the quicksilver mines of Idria 
and California, Nevada and the Bavarian Palatinate; in the zink 
mines at Ammeberg in Sweden; in the copper mines of Schmoell- 
nitz in Hungary; in the pyrites mine at Meggen in Rhineland; in 
the iron mines atWermland in Sweden, where the gneiss is colored 
by bitumen, containing sometimes as high as ten per cent, of bitu¬ 
men; in the copper veins at Parad, Hungary; in the zinc mines in 
Baden; in the manganese mines in Nassau; in the silver mines in 
Schwarzwald; in the kaolin of selvages; in the lead mines of Derby¬ 
shire, etc., etc. Thus, there was no want of organic matter for 
percipitating the sulphides of metals. 

Professor Sandberger successfully demonstrated that the con¬ 
tents of the veins crossing crystalline rocks in some mining dis¬ 
tricts of Germany, were derived from these rocks. 

In some cases the metalliferous silicates and sulphides and the 
microscopic cavities contained in the crystalline rocks which, in 
some districts, gave birth just to the biggest and richest ore-depos¬ 
its known, were sufficiently supplied with the elements for these 
deposits. In other cases the mineralizing waters which had to 
produce them may have come ft-om Magmas from which the erup¬ 
tive rocks had arisen, or came from deep seated ore-deposits; or 
had gathered their mineral substances by reaching some other 
zones of rocks, and we do not know the limits of the reactions of 
steam evolved from intrusive rocks when cooling under pressure. 

“The deep seated plutonic rocks, for instance Granite, Syenite> 
Diorite, have crystallized from a state of magma at great depths, 
and occur in the form of large irregular masses, from which dykes 
and veins may or may not have proceeded. The magmas from 
which the dykes of our own age proceed, will consolidate by and 


4 


by, and other magmas will originate as the scene of volcanic action 
has been continually shifting to fresh areas at different periods of 
the earth’s history. Geologists have revealed for inspection and 
study the masses of originally fluid materials, from which one or 
more volcanoes have been fed, cooled and consolidated in their 
original reservoir. There are many examples of masses of granitic 
or highly crystalline rocks having precisely the same composition 
of the different varieties of lavas, which are found lying in the 
midst of the sedimentary rocks, and sending off into these rocks 
dykes of the same composition with themselves. No one who has 
carefully studied the appearances presented by volcanic mountains 
in different stages of dissection, by the action of denuding forces, 
can avoid recognizing these great granitic masses as the cooled re¬ 
servoirs from which volcanoes have been supplied during earlier 
periods of the earth’s history. In those subterraneous regions, 
the silicates have been iDlaced under conditions especially favor¬ 
able for the action of crystalline forces; they must have been under 
an enormous pressure, produced in part by the weight of the 
superincumbent rocks, and in part by the expansive force of the 
imprisoned steam.” (Judd-Volcanoes.) 

During this process of crystallization, the metallic substances 
contained in the superheated magmas were either ejected into As¬ 
sures, or retained in the consolidating magmas. Later they may 
have been brought to higher horizons by the chemical activity of 
percolating waters. 

Examples of Ore-Deposits Directly Occurring in Erup¬ 
tive Kocks. 

1 A. In Nijni-Tagilsk, Ural Mountains, nuggets of iDlatinum 
and gold are found enclosed in nuclei of olivine occurring in 
debris of serpentine. The jplatinum is alloyed with metallic iron, 
and is magnetic. The olivine being an anhydrous silicate of mag¬ 
nesia, is by taking-up water, changed to hydrated silicate of mag¬ 
nesia, called serpentine, a word too often incorrectly used. Olivine, 
of the speciflc gravity of about 3.4, is one of the constituent min¬ 
erals of meteorites and some erruptive rocks, the speciflc gravity 
of which is higher than that of other rocks; it belongs to the ma¬ 
terials of the great depths in our earth. In this example, it seems 
that we have the primitive occurrence of a metal before us, primi¬ 
tive in the same sense as we use this word of limestones or of coal. 


o 


In all the platinum-deposits of the Ural, the serpentinous rocks are 
always most productive of this metal, 

IB. A similar case of primitive occurrence of a metal is the 
native iron which can be obtained by the ton in Ovifak, Grreen- 
land, which district has been the scene of volcanic outursts on the 
grandest scale during the Tertiary age. As the basaltic rock in which 
it occurs, was taken off on outcrops by denudation, and as the iron 
is alloyed with nickel and cobalt, it was at first mistaken for me¬ 
teorites. These large iron masses, as well as the particles of me¬ 
tallic iron, diffused through the surrounding basalts, have been 
brought by volcanic action from the earth’s interior. Certain ba¬ 
salts in England contain particles of metallic iron of miscroscopic 
dimensions. 

IC. A similar occurrence of metallic iron is that of Gran 
Choco, Argentine Republic, containing ten per cent of nickel. 

2. The Katsch Kanar Mountain in the Ural consists of 
augitic porphyry surrounded by serpentine; the rock is entirely 
streaked with nuggets and small veins of magnetic iron ore. Augite 
containing about eleven per cent of protoxide of iron, is a con¬ 
stituent mineral of some eruptive rocks; the process of its decom¬ 
position has been demonstrated by the microscope. In that vicinity 
is the mountain Gora Blagodad, consisting of augitic porphyry, 
containing great masses of magnetic iron ore. This mountain is a 
good example for showing what changes in physical appearance 
one and the same eruptive rock has experienced by cooling, by 
losing its steam, and by decreasing pressure. Thus our former 
empyrical petrographists .called the rock in the lower parts of the 
mountain augitic porphyry, higher up uralite, and near the top 
basalt. 

3. The Iron Mountain in Missouri consists of Malaphyre, 
with large segregations of specular iron; the latter is a constituent 
mineral of the Melaphyre, an igneous rock. 

4. In the well known deposits of magnetic and chromic iron 
ores segregated in serpentine of different countries, it is obvious 
that the quantities of segregated ore are there in proportion to the 
degrees of decomposition of olivine. 

5 A. One of the puzzles for geologists is the ore deposits of 
Monte Calvi, in Tuscany. Two dykes of Augite, seventy to one 
hundred and twenty feet thick, crossing a sediment of white 
marble, show a globose structure; the globes are from one-half 


6 


inch to eight feet in diameter, but their structure is both concen¬ 
trically radiated and concentrically shell-like. The center is filled 
with iron and copper pyrites, with zinc blende and galena, with 
which ores also other parts of the augitic masses are streaked. 
These dykes are crossed by dykes of quartz-porphyry and of aug¬ 
itic porphyry. A high state of metamorphism must have taken 
place in that district. Under metamorphism, I understand me¬ 
chanical energy converted into heat with its chemical conse¬ 
quences. The degree of this heat is, according to well known 
experiments, far from being intense, if water and alkali be present, 
and act under pressure. 

5 B. A similar occurrence is the vein of green Pitchstone at 
Chiaja di Luna, in the island of Ponza, Italy; breaking up into 
regular columns, and into spherical masses with a concrete series 
of joints. 

6. In the Diabase-veins at Zorge, in the Harz Mountains, the 
decomposition was so energetic that in themselves fractures and 
fissures were formed, even extending sometimes into adjacent 
slates; in the latter case showing no ores. The veins manifest 
that chemical energy by many slickensides, caused by pressure. 
Diabase rock consists of Plagioklase and Augite; the latter furn¬ 
ished the ore also in this case. * 

7. In undecomposed Diabase of Nassau, in Germany Pro¬ 
fessor Sandberger detected copper. In the decomposed Diabase, 
the segregations of copper jDyrites are so much richer, the more 
this rock has been decomposed; and the same veins of that dis¬ 
trict are free of ore, wherever they extend into adjacent slates and 
sandstones. 

8. The celebrated copper ores of Chile have replaced a part 
of the diorite in its dykes; their foot-wall shows a selvage consist¬ 
ing of the materials of former diorite, while in the hanging wall 
the ore appears grown together with the rock. Such veins often 
originated by fault-fissures. 

9 A. At Kaafjord, Norway, there is a fault between archaean 
and paleozoic schists, and filled by a dyke of diorite, which con¬ 
tains a vein, sometimes fifteen feet thick of breccia, consisting of 
quartz, calcspar and copper pyrites cemented together by a slime 
consisting of the materials of diorite. Wherever this vein meets 
the paleozoic slate, it is poor in copper. 

9 B. The newly discovered silver veins at Creede, Colorado, 


7 

occupy fault lines between two different kinds of eruptive rocks. 
They are true fissure-veins. 

10. The Peninsula of Keweenaw, Lake Superior, belongs to 
a district where a great accumulation of sediments had taken place. 
The strata of the Lower Silurian period have been interbedded by 
a complex system of st^j^ita of diorite, melaphyre and amygdaloidal 
melaphyre, containing beds of conglomerates. The intrusion of 
these eruptive rocks, and the deposition of the conglomerates mtist 
therefore have taken place during the same period. In a right 
angle to the length of the Peninsula there are numerous vertical 
veins from a few inches to thirty feet in thickness, crossing all 
those strata, and being filled with quartz, calcspar and other 
gangue minerals, but where they cross the malaphyres, also with 
native silver and masses of native copper, weighing, sometimes, 
eight hundred tons; those veins are also filled with numerous 
braccias of melaphyre. Wherever they cross the diorite, or the 
adjacent sandstones and conglomerates, they are free of those two 
metals, but contain zinc ores. The amygdaline cavities of the me¬ 
laphyre often appear to have been filled with silver and copper; or 
partly with the same gangue contained in the veins, even far dis¬ 
tant from these fissure-veins. Within the melaphyre there occurs 
a breccia of felsite-porphyry cemented by a material consisting of 
silicates of magnesia, calcspar and native copper, the latter in wire 
form or dentritic; but as the copper was never found in the frag¬ 
ments of the breccia of the felsite-porphyry, only in the cement, 
its latter formation is clearly demonstrated. The close paragenesis 
of silver and copper without being alloyed, contradicts every hy¬ 
pothesis in regard to high temperatures. The silver andcopj)er must 
have been present only in the melaphyre. Perhaps carburetted 
hydrogen was present in the pecolating waters, by which the 
metals were precipitated as such. As Olivine and Augite are con¬ 
stituent minerals of melaphyre, and are identical in composition 
with some meteorites which contain also carbonaceous matter and 
different gases, it may be presumed that hydrocarbon had been 
in the melaphyre, as it was found in the minute cavities of crys¬ 
tals in crystalline rocks. Besides, the waters when percolating 
through the strata of the Lower Silurian period, might have taken 
up some carburetted hydrogen from their carbonaceous matter, in 
a similar manner as the mineral oil of carbonaceous shales was 
taken up in the gaseous state by the trap of the Connecticut 


8 


valley and deposited in an oxydized condition in the amygdaloidal 
cavities, where it now occurs in black coal-like nodules. The 
bringing-up petroleum to the surface by volcanic influence can be 
seen at this very day, at Baku, where petroleum occurs in a porous, 
argillaceous sandstone of Tertiary age. In the vicinity are hills 
of volcanic rocks, through which springs of petroleum flow out. 
Compounds of copper with sulphur or oxygen are of very rare oc¬ 
currence in those mines. The gangue minerals were formed at the 
end pf that mineralizing process; “their crystals are implanted on 
or about threads of copper, showing that they are of subsequent 
origin.”—(Dana, Geology.) 

11 A. The eruptive rocks of the Tertiary era are the matrix 
of the ores occurring in many celebrated mines in Hungary, Tran¬ 
sylvania, in the Bocky Mountains, in Mexico and South America. 
There, petroleum and Tertiary plants were also found in the rocks. 
The ore-deposits in the eruptive rock (Propylite) of Scheiiinitz, 
Hungary, belong to the largest deposits known; they are some¬ 
times one hundred and thirty feet thick, and followed for a dis¬ 
tance of flve English miles. These ore-deposits are very numerous 
in the Propylite of Schemnitz, and their ores appear mostly con¬ 
centrated in lenticular masses (chimneys.) They are no fissure- 
veins, but zones filled with ores and numerous large fragments of 
the rock, which strikingly exhibit a high degree of decomposition, 
while the ores are found not only around them as cementing ma¬ 
terial with the gangue and rock fragments, but also within the 
fragments themselves, a clear proof that the materials of the i)ro- 
pylite were changed by the materials of mineralizing waters. In 
some lodes in Hungary the paragenesis of sulphide of Antimony 
which can be fused at the flame of a candle, with Heavy Spar en¬ 
veloping the former mineral, proves that the spar had crystallized 
out of a watery solution, as the crystals of the sulphide could not 
have been preserved in dry fusion. The ore-deposits are not be¬ 
tween well defined limits, and no selvage can be observed. 

Professor Sandberger found that the eruptive rocks are richer 
in metals the later the age of their formation; the richness of the 
dark micas of the propylite of Schemnitz in heavy metals is quite 
remarkable. 

11 B Quite similar is the general character of the celebrated 
Comstock Lode in Nevada, which was greatly changed in the zone 
of oxydation, and shows selvages sometimes twenty feet thick. By 



9 


Sandberger's method, the constituents of the rocks of this lode 
have been investigated. The augite in the diabase contained the 
larger proportion of a notable amount of the precious metal. “The 
decomposed diabase contains about one-half as much of these 
metals as the comparatively fresh rock. The relative quantities of 
gold and silver, both in fresh and decomposed diabase, correspond 
fairly well with the known composition of the Comstock bullion. 
The total exposure of diabase is sufficient to account for far larger 
quantities of bullion than have been extracted from the mines.” 
—(G. F. Becker, The Comstock Lode, Washington, 1882.) “The 
filling of the Comstock occupied two distinct periods, a siliceous 
and a siliceous-argentiferous one, separated by formidable geologi¬ 
cal events.” “There is a noticable difference between the charac¬ 
ter of the quartz in the rich and the barren portions. The rich 
quartz is milky white sugar-quartz capable of comminution by 
rubbing between the fingers. The metallic contents consolidate 
the sand.”—(Dr. Church. The Comstock Lode.) 

“Abundant drifts in these mines opened on the Comstock 
Lode rapidly close up from the pressure of the ground which had 
an extraordinary tendency to move and fill up any openings that 
are made in it.”—(Dr. Church. The Comstock Lode, 1879.) 

The formation of selvages in these mines is still going on in 
the layers of fissured rock, which are the hot belts and the reser¬ 
voirs of water, and are found to act as the furnaces of the district. 

No explanation has been found yet for the occurrence of un- 
silicified wood in the Sutro Tunnel, and in the shafts sunk to meet 
the tunnel. 

12 A. Several of the very numerous ore-deposits in the Altai 
Mountains are worked in porphyry, being replacements of 
porphyry. 

12 B The celebrated Sheridan vein near Telluride, Colorado, 
does not occur entirely in eruptive rock, as some papers stated, 
but it is a contact-vein originated by a fault, therefore a fault-vein. 
But the vein matter consists of more or less decomposed country 
rock, partially replaced by silica and ore. 

13. Professor Sandberger has demonstrated that all lithion- 
mica contain tin, no matter in what region they are found, and 
that the tin-ore-deposits are the products of the decomposition of 
crystalline rocks which had contained such mica. 

The half decomposed gneiss and some schists of the Silurian 


10 


and Carboniferous above Manitou, Colorado, contain Lithia, and 
so do the Manitou Springs. In that gneiss, also Molydenite is 
found, which is paragenetic with tin ore in tin mines. 

Examples of Ore-deposits Occurring in Stratified Rocks. 

14. Near Rio Albano, Elba, Italy, talcose-slates have been crossed 
by veins containing specular iron and fragments of the slates; the 
veins are also ramifying through the slates, which contain spheres 
of ore four feet in diameter. On the top, the veins spread out in 
the form of beds covering the top of the mountains. A similar 
occurence of overflow is observed on the iron vein of Capo Cala- 
mita, Elba, Italy. (See No. 28.) 

15 A. There are many ore-deposits in the contact zone between 
granite and stratifled rocks, in which the former work of mineral¬ 
izing waters can be observed; for instance, in the Pyrenees, there 
are three contacts, one between granite, and paleozoic limestone, 
annother between granite and Jurassic limestone, and one between 
granite and cretaceous limestone; but one and the same kind of 
ore-deposits was found in these contacts. 

15 B. At Christiania, Norway, big ore-deposits are found in 
the contact zone between granite and silruian slates. 

15 C. The zone of contact between granite and slate has a 
very favorable influence on the development of the ore-veins of 
Cornwall, England. 

Ore-deposits are very common between eruptive rocks and 
sedimentary formation, but it is remarkable that the most of this 
kind occur between the former and limestones, and that the sur¬ 
faces of the eruptive rocks appear the most altered, if the stratifled 
rock is of a calcareous or carbonaceous nature; the eruptive rock 
loses its dark color, assumes tints of i^ink and green, or even be¬ 
comes quite white, and chemical analysis show that such altered 
eruptive rocks contain from nine to ten per cent of carbonic acid, 
and ten to eleven per cent of water. 

15 D. At Schwarzenberg, Saxony, a cone of granite is sur¬ 
rounded by gneiss and micaslate. The annular contact-zone be¬ 
tween these rocks is fllled with a green mass of protogine in which 
the ore is enclosed. This protogine is a decomposed eruptive 
basic rock which occurs in the micaslate, and almost parallel to 
its schists, and follows lenticular masses of limestone enclosed in the 
micaslate. This contact zone is rich in ores, and especially in cer- 






11 


tain silicates which are so often found in places where contact- 
metamorphosis had taken place. The ore has replaced some of 
the limestone. 

16. In the Reveille Distriat, Nevada, the dolomites are crossed 
by i^orphyries. The former are replaced by numerous irregular 
ore-segregations carrying rich silver ores. 

17. At Rio Tinto, Spain; paleozoic clayslates contain parallel 
intrusive masses of quartz-porphyry and diorite. The slate stands 
nearly vertical, and contains lenticular masses of pyrites. Its 
physical appearance next to the ore is much changed by contact- 
metamorphosis, being there much streaked with quartz. The de¬ 
composition of the pyrites by the oxydizing meteoric waters is still 
very strong; it has been calculated that, during the past fourteen 
hundred years, eighty thousand tons of copper, and five hundred 
thousand tons of iron have been leached from the pyrites and 
carried into the sea by the river Tinto, in the state of sulphates. 

18. The quicksilver deposits in the Bavarian Palatinate and 
in California are striking examples for the production of ore-de¬ 
posits by percolating mineralizing waters gradually replacing the 
materials of the rocks. In the Palatinate, diassic slates and sand¬ 
stones have been crossed by porphyries. The ores are mostly in 
the zone of segregation of silica and silicified clay, but also in the 
sandstones and conglomerates and in the porphyry itself; but the 
slates contain the ores only where casts of fish-fossils occur. The 
cretaceous shists in the California coast range have been crossed 
by eruptive rocks, rich in silica of magnesia; in these and near 
their contact the quicksilver ore occurs. 

19. In the contact zones between Syenite, Micaslate, and 
Dolomites, at Traversella, Piedmont, Italy, the products of min¬ 
eralization are magnetic iron ore, garnet with dark hornblende, as¬ 
bestos, and, in the vicinity of the dolomite, spathic iron. The ore- 
deposit sometimes shows banded structure and many drusy cavi¬ 
ties containing crystals indicating that the former mineralizing 
waters were almost stagnant. 

20 A. The auriferous quartz-deposits in Australia are en¬ 
closed in sedimentary and eruptive rocks and accounted for by the 
mineralizing waters which followed the eruption. The quartz- 
[20 B.] deposits in New Zealand are similar, while those in Cali¬ 
fornia [20 C.] (not the placer deposits) were caused by the min¬ 
eralizing waters which followed the eruption of granite. It i^ 


12 


notable that the latter deposits are much poorer in silver than the 
deposits derived from other eruptive rocks, and that even for their 
gold they are not adapted to more than a temporary profitable 
mining. 

21 A. In the vicinity of Mansfeld, Germany, Melaphyres oc¬ 
cur. The copperslate of Mansfeld originated by mineralizing solu¬ 
tions emptying into a shallow bay largely populated by fish, the 
casts of which showing the bodies in a convulsively contracted 
condition, which indicates that poisoning was the cause of their 
death. The bodies decaying in the slime of that bay which formed 
the present copperslate, produced the bitumen for the reduction of 
the copper solution. 

21 B. A like circumstance may have caused the lead ore-de¬ 
posits of the Upper Mississippi, in which we find neither much 
silver nor quartz, nor compounds of lead with arsenic and phos¬ 
phorus. These ore deposits are irregular zones of replacements of 
dolomite; this region has an extent of over twenty-five hundred 
English square miles and its mineralization took place during the 
latest geological periods, as we find bones of elephants and masto¬ 
dons cemented together by coarsely crystalline galena. Carbonate 
of zinc constitutes also pseudomorphs after calcspar in that dis¬ 
trict. 

If dolomite has been originated by the interference of bicar¬ 
bonate of soda contained in metalliferous springs issuing into the 
sea-water, it will be of a metalliferous character itself, and liable 
to further decomposition. 

22. The lead-ore-deposits of Derbyshire and Cumberland in 
England seem to have been caused by mineralizing waters after 
the eruption of the Toadstone, a rock like diabase lying in intrusive 
beds between the shists of the carboniferous limestone, which has 
been fissured in different directions after the intrusion of the Toad- 
stone. It is remarkable that petroleum occurs in that limestone 
and that the richness of the ores in the deposits is confined only 
to the limestone, but not to the slates, nor to the dia base. It is 
remarkable that these lead ores are very poor in silver, and that 
the gangue consists of marly, sandy, conglomeratic agglomerations 
in which petrified organisms were discovered belonging not only 
to the carboniferous age, but some to the younger Lias period, 
which circumstance shows that the fractures of the limestone were 
filled by water-currents from above. 






13 


In using so often the expression “mineralizing waters,” I 
mean, firstly, descending meteoric water with absorbed carbonic 
acid, air and organic matter; secondly, ascending thermal alcalical 
springs, and their connections with exhalations of carbonic acid, 
sulphuretted hydrogen and sulphurous acid; and with the deep 
sea. Such mineralizing waters have been started by volcanic 
action. 

The Oee Deposits of Leadville. 

23. Before the elevation of the Mosquito Kange and before 
the Blue Limestone Avas overlaid by the other beds of the Carboni¬ 
ferous period, the limestone had the consistency of the sea-bottom 
of our time, in and ui^on which the remainder of marine organisms 
had been accumulating as a scource of petroleum, as they do in 
our days. The silicic acid contained in the sea-water was by the 
help of the organic substances transformed into concretions of 
black chert, which we find containing within their mass distinct 
casts of fossils. Many of those concretions were split during the 
subsequent period of folding and faulting, forming “dislocated 
breccia,” for instance, in the Smuggler mine. According to the 
statement of Mr. Emmons of the L^. S. Geological Survey, that 
Blue Limestone is of a remarkable regular composition, of that of 
normal dolomite, containing a very small percentage of silica, its 
fossils are comparatively abundant in its. upper beds. It was espe¬ 
cially this zone, into which after the deposition of the upper sedi¬ 
mentary beds, the eruptive rocks effected their intrusion.- Ages 
after, in the Postcretaceous period, that great mountain-making 
period commenced, “during which in North and South America, 
as well as in Europe and Asia, mountain ranges were raised over 
ten thousand feet.” (Dana-Geology.) It was initiated in this 
region by those dynamic movements which may still be going on 
according to indications being observed in some Colorado mines, 
for instance, in the Colorado Central mine above Georgetown. 

The metals found in the deeper parts of the deposits, beyond 
the influence of the alterations done at a later period in the zone 
of oxydation, are in the state of sulphides (pyrites, argentiferous 
galena and zincblende). These ores must have derived from the 
same magma from which the porphyry dykes had proceeded, be¬ 
cause the sedimentary beds before the time of mountain-making 
were more or less horizontal, and so were the intruded sheets of 


14 


porphyry, from which the heavy ores segregated, according to the 
law of gravity, at its lower side. There were no waters percolating 
yet through these horizontal plastic sediments ten thousand feet 
below the bottom of the former ocean. But under this pressure, 
there was superheated steam, that powerful destroyer of cohesion, 
that chemical promoter of decompositions and recompositions. 
But after those dynamic movements the quantity of these ores 
was augmented by the action of percolating waters gradually re¬ 
placing the Blue Limestone, the thickness of which is found to be 
proportionately reduced if the amount of replacement has been 
exceptionally great. 

No indications of pre-existing fissures can be observed. The 
geological circumstances of the faulted beds, and the fact that the 
faults contain no ore, excepting attrition material, or small infiltra¬ 
tions of secondary minerals, demonstrate that the original ore-de- 
position took place after the intrusion of the eruptive rocks and 
before the folding and faulting occasioned by the great dynamic 
movement. Taking into consideration that the physical appear¬ 
ance of the overlying porphyry is, with the exception of the con¬ 
tact-line, near the ore body, quite compact and homogeneous, and 
that the volumes of the decomposed porphyry and of the ore bodies 
are in a contradictory proportion, and considering that “instances 
of the diversions of ore-currents into the mass of the Leadville 
porphory are extremely rare and even then, the ore is of secondary 
origin;” (Emmons Beport.) one feels that it is rather difficult to 
reconcile these facts with that theory: that the Leadville ore-de¬ 
posits as they were deposited in their original form before the 
period of folding and faulting derived their metallic contents from 
the neighboring porphyry by aqueous solutions which came from 
above. But, according to the analyses made in the Laboratory of 
the U. S. Geological Survey, we do know that the average propor¬ 
tions of silver, galena and iron ores contained in the Leadville 
pyritiferous porphyry are the same as those of the Leadville ores 
as a whole, therefore, they must have come from the same source, 
from the same magma, from which the porphyry had proceeded. 

In consequence of the numerous faults product in that dis¬ 
trict, numerous outcrops of the primitive ore-deposits have been 
created; the leaching by the meteoric waters was therefore much 
facilitated, but it had to be effected through the detritus caused by 
the destruction and the erosion of rocks lying above the outcrop. 



15 


So immense was this erosion that it left on “ Fryer Hill ” only 
eighty feet of porphyry, while this rock had solidified, according 
to Mr. Emmons, under the pressure of a thickness of at least ten 
thousand feet of superincumbent beds, and of the depth of the sea. 
The meteoric water filtering through these fragmental masses cer¬ 
tainly had the best opportunity beside its carbonic acid and air to 
become a solution of carbonates and alkalies, chloride of sodium 
and other salts, which could not fail to decompose the detritus and 
its metallic contents, and to carry their solutions down to the lime¬ 
stone, rich in organic matter, and to cause those immense wedge¬ 
like replacements which were out-croping during the best days of 
Leadville’s time; and we should not wonder that the richest second¬ 
ary ore-deposits of that district have been developed just on 
“Fryer Hill” where not only this great erosion had taken place, 
but where also the limestone offered more surfaces, as the porphry 
has split the white limestone into three sheets which, having been 
replaced, form as many different ore bodies. 

There was certainly no want of carbonaceous matter for de¬ 
composing the metallic sulphates leached in the detritus; no want 
of alkaline carbonates and chlorides to produce carbonate of lead 
and chloride of silver. But as the undecomposed galena left in 
th.e outcrops contains considerably more silver than the carbonate 
of lead, derived from it, what became of the silver? It seems to 
have been incorporated in the great masses of iron ore, and partly 
to have impregnated the dolomite. When three bore-holes were 
drilled in the New Discovery mine of the Little Pittsburg Co. by 
a diamond drill in the year 1879,1 assayed the cores for silver, using 
large quantities and concentrating the buttons, as often as the 
men struck a different material. With two exceptions, all the 
cores yielded some silver, from one-half ounce up to ten ounces 
per ton. The cores were taken at a great distance from the ore- 
deposit and some quite near the lower quartzite. The chloride of 
silver in the Kobert E. Lee mine is a repeated secondary deposi¬ 
tion, as we know by Mr. Emmons’ report. 

Here another question presents itself. As the galena, when 
altered to carbonate, increases twenty-eight per cent, in volume, 
how was room made for this great increase? Since the process of 
secondary depositions has been going on, the contact-materials cer¬ 
tainly were of a softer condition, and besides, some additional 
room must have been gained in consequence of the chemical inter- 


16 


change of the ironpyrites and the dolomite, by which the latter 
was replaced by carbonate of iron, which we find subsequently 
changed to oxide of iron. 

The Leadville ore-deposits have often been explained to be 
contact veins; this is not correct, as in a contact-vein the two wall 
rocks differ in their character. The Leadville ores are not con¬ 
stantly found between porphyry and limestone, but also in differ¬ 
ent horizons of the limestone, as the mineralizing winters percolated 
and caused replacements in the limestone, wherever they found 
access, which was surely the case in the bedding plane, and where 
the most organic matters had been accumulated. The vein material 
of those deposits which have been changed in the oxidized zone is 
more siliceous than that of the deposits in the limestone of the 
lower horizon. 

Our miners will perceive that the ores of. the lower geological 
horizons of the Leadville district, for instance, of the Col. Sellers, 
the Silver. Cord, the Minnie, and some ore-deposits on the other 
side of the Mosquito range, for instance, in the Mosquito, Buck¬ 
skin and Pennsylvania gulches, represent the’ primitive character 
of all the ore-deposits in the Mosquito range, and may be the 
source for further mining. 

Oee-Deposits at Aspen Mountain. 

24. Like in the Leadville district they belong to the Blue 
Limestone of the Lower Carboniferous, but, instead of being 
directly under the porphyry (Diorite), the deposit is about one 
hundred and seventy feet below it; in a zone between the Blue 
Limestone and the underlying dolomite, while the Blue Limestone 
is not dolomitic, but a pure limestone with about ninety-five per 
cent, of carbonate of lime. 

Along that bedding plane, an easier access was offered to 
mineralizing waters, which cannot have leached the overlying por¬ 
phyry, as the physical appearance of this rock and the upper parts 
of the limestone and the black shale, which lies between this and 
the porphyry, show no indications of mineralization in a manner 
similar to that in the zone of the ore-deposit. The occurrence of 
the ore in regard to its distribution, does not admit the presump¬ 
tion of a pre-existing fissure; the limits of the ore-bodies are so 
indistinct that the miners have to be guided by assays, so different 
is the degree, so irregular the zone of replacement. 


17 


The primitive character of these deposits has not yet been reached 
as the mines are not deep enough; in the deepest workings of the 
present time one may observe more or less distinctly three different 
periods of ore deposition. This zone of the lode obtained its char¬ 
acter after the time of folding, by which dynamical movements the 
access of meteoric water was facilitated which filtered through the 
detritus of the porphyry, and leached its minerals which we find 
to-day in replacements. In consequence of the dynamical move¬ 
ments the meteoric waters could not only percolate between the 
bedding plane, but found also cross fractures for their work to 
form secondary ore-deposits. 

Therefore we should not wonder if we find the value of the 
ore-deposits changing so much throughout this zone. 

As the lode dips from thirty degrees at the surface to sixty 
three degrees at the deeper mines, the silver leached from the lead 
ore in the upper parts was not so easily lost in the masses of dolo¬ 
mite as it was in the Leadville district, but carried down and de¬ 
posited again in new replacements; thus we find the greatest rich¬ 
ness in the deeper ore-deposits, and their size increasing with the 
depth; indications which are highly promising for the future of 
Aspen. The primitive character of the Aspen ore-deposits cannot 
be reached before striking the contact of the dolomite with the 
vent of the porphyry. 

As Baryta was found in the argentiferous porphyry of Aspen,- 
it is not astonishing to find heavy spar in the lode, sometimes in 
banded structure, which is quite common in deposits of the “Bary- 
tic Lead-formation,” and is no particular privilege for fissure-veins 
only. 

It is an illusion to regard the fissure-veins as somewhat of an 
aristocracy among the other deposits, and to try to give this title to 
simple replacements. It is high time to use such terms in a more 
correct manner. A fissure-vein is not only a flat-shaped ore body 
between well-defined walls, but the ore body is supposed to have 
been caused by the filling-out and widening-out of a pre-existing 
fissure. Not every vein is a fissure-vein; one can speak of a vein 
as of a deposit and its zone, just as the coal miner speaks of his 
coal vein, instead of coal-bed; but deposits so easily proved as re¬ 
placements should never be called fissure veins. 

The word “lode” ought to be used by miners only collectively. 
Any geological zone in our earth carrying metals or metalliferous 


18 


minerals, may be called a lode. The words “lode” and “ore- 
deposit” are synonyms in geological regard; but in technical re¬ 
gard, an ore-deposit is a lode the technical value of which has 
been proved already. 

25. The celebrated gold and silver mine, Veta Madre, at Guana¬ 
juato, Mexico, occupies a line of fault between the Devonian clay- 
slate and Diassic conglomerates, of a thickness of almost five hun¬ 
dred feet, with ore iDockets of one-hundred and thirty feet thick¬ 
ness. It is, therefore, a fissure-vein. 

The gangue consists of amethyst and calcspar, also of spathic 
iron and fluorspar. Heavy spar is entirely absent. The selvage 
consists of lithomarge, indicating that a high degree of decompo¬ 
sition obtained. The deposit is in no visible connection with the 
porphyry in its vicinity. But we know where amethyst and other 
gems were mostly originated, therefore we cannot be in doubt 
about the genesis of this lode; in other words, the fissure had been 
caused by the eruption of the porphyry, and was then filled out by 
the activity of mineralizing waters. 

26. The ore deposit of Fahlun, Sweden, is enclosed in mica- 
slate. The lenticular bodies of copper pyrites are enclosed in a 
corroded quartz, mixed with magnesia silicates and breccias of 
diabase and limestone. There is no distinct boundary between 
the ore-deposits and the wall-rock. The ore-deposit may be a 
replacement of a former bed of limestone. 

27. The celebrated spathic iron deposits in the Alps of styria 
are mighty'replacements of Silurian limestone by the spathic iron. 
Those in the Carrinthian Alps .are replacements of limestone 
belonging to the Archaean era. 

28. (See No-. 14.) Great iron-deposits on the island of Elba 
are underlaid with talcose slate, and overlaid with crystalline lime¬ 
stone, The director of the Geological Survey of Italy has demon¬ 
strated that they are the products of replacement. 

29. The lenticular pyrites deposits at Schmoellnitz, Hungary, 
occur in a zone of black clayslate which is over one thousand feet 
in thickness, rich in carbonic substances, but less carbonaceous 
along the zone of the ore-deposits, which circumstance exj)lains its 
genesis. 

30. Near Trondhjelm, Norway, irregular pyrites deposits are 
imbedded in Huronic slates, and interchange with them. Where 
the ore pinches out, quartz is in its place. The pyrites still contain 





19 


up to 2.6 per cent, of carbonic substances, and the slate is often 
changed to alunite-slate. In some places the deposit looks like a 
conglomerate of slate fragments and ore. 

31. At Ducktown, Tennessee, three zones of lenticular ore- 
deposits are imbedded between talcose and micaslate without a 
distinct boundary. In the lowest part of each zone, the primitive 
vein-stone with copper pyrites predominates; higher up, iron 
pyrites; with the waterlevel the zone of oxydization coincides; 
there is at first a zone of oxydized copper ores, and above, one of 
oxydes of iron. The rocks appear to contain such ores themselves; 
in the neighborhood, sx^rings with sulphuretted hydrogen arise, 
and the miners were sometimes driven out by this gas. The most 
copper was found wherever in the wall-rock a fracture of a down¬ 
ward inclination was terminating at the deposit. These ore- 
deposits are probably replacements of former lenticular deposits of 
crystalline limestone, so often occurring in the Archaean rocks. 

32 A. The Devonian Slates at Meggen, Rhineland, are inter- 
bedded with beds of pyrites and of Heavy Spar. Both minerals 
contain carbonaceous substances. 

32 B. Similar to this deposit is the Rammelsberg ore-deposit, 
Harz Mountains, Germany. It contains many lenticular bodies of 
XDyrites, and its former bed-materials had been originated before 
the upheaval of the mountains, as all the contortions of the sur¬ 
rounding rocks are shared by the x^resent ore-bed itself. Although 
it is in no visible connection with an eruptive rock, one may 
expect that an investigation by Sandberger’s method will x^rove 
it to be a replacing dex^sit in the Devonian clayslate,. viz: that 
the ore-bodies have been formed by the mineralizing waters 
entering after the erux:)tion of the diabase occurring in the clay- 
slate. 

33. The quicksilver dex^osit of Idria consists of a bituminous 
Triassic clayslate rich in corals and shells, and contains the 
different ores, together with x^yrites, graxfiiite, anthracite and bitu¬ 
men. It is overlaid by a dolomitic conglomerate, and this by a 
clay slate, both of which -sometimes carry quicksilver ores, the 
latter even metallic mercury. There a great fault occurs; and a 
tuffa underlying the deposit indicates that there was solfataric 
action at work. Presently the mine is growing richer as greater 
depth is attained. 

34. The copper sandstones of the Perm period in Russia con- 


20 


tain many fossils of tlie vegetable kingdom. Their copper is in 
the state of oxyde and its compounds; but wherever it came in 
contact with the fossils, it was changed to sulphide. These copper 
sandstones derived from the copperiferous rocks in the Ural 
Mountains have an immense extension in Russia, while in the 
whole European part of Russia (except in Poland) there are no 
lead ores of some amount. 

35. The conglomerates and the coarse lower sediments of 
sandstones at Commern in the Eifel Mountains, Rhineland, con¬ 
tain ore-beds of knotted and cemented quartz and ore. The knots 
of the ore appear only where the quartz-grains are white (free of 
carbonaceous matter); when they are colored, there is no ore. 

36. To the schists of the Lower Silurian in the United States 
belong dolomites which, at various places, for instance, at Knox¬ 
ville, Tennessee; at Austin, Virginia; and Friedensville, Pennsyl¬ 
vania; at Rossi, New York, inclose deposits of lead and zinc ores 
in a manner that the books acknowledge the primitive existence of 
lead and zinc combinations in their present enclosing rock. These 
combinations, they say, were formerly as finely reduced as the 
particles of the dolomite before consolidation, and afterwards con¬ 
centrated in isolated cubes and nuggets of galena, and, at Austin, 
Virginia, accumulated ' in pockets in three beds consisting beside 
the ore, in dolomite with quartz and limestone. Each bed is 
underlaid with a bed of zincblende three feet in thickness. But 
that fine reduction process and that concentration taking place 
after the consolidation, are rather mysterious actions. Should we 
not better suppose that those dolomites were originated by the 
carbonates of springs which so often contain metals in solution? 
That concentration was only a consequence of the irregular distri¬ 
bution of organic matter before reactions took place. 

At the end of these examples the “fahlband-deposits” may be 
mentioned. They are sedimentary ore-deposits consolidated con¬ 
temporaneously with the enclosing schists, and afterwards meta- 
morphozed. They are often observed in chrystalline rocks; for 
instance, the auriferous pyrites in the Rauris, near Gastein, Aus 
trian Alps. The fahlbands when crossed by metalliferous veins, 
had an ennobling influence on the richness of the latter; for 
instance, at Kongsberg, Norway. The gneiss in the Fall River 
Gulch, Clear Creek County, Colorado, contains a great fahlband 
extending for several miles west to the Berthoud Pass, the glitter- 




21 


ino: iron-pyrites of which have induced to frequent prospect holes, 
and even to the too hasty erection of mills. 

Some Special Examples of Oee-deposits in Fissure-veins. 

Taking into consideration that, according to physical laws, 
the thickness of our earth’s crust must be far greater than that 
which the childish arithmetical example requires, based on the 
theoretical average increase of temperature with depth, if there be 
any general liquid interior at all, the often heard talk about 
fissure veins reaching down to that region of general fusion is 
absurd, while even their length amounts generally to only four 
English miles, and in rare cases to sixteen miles. By observation 
with the Seismo chronograph it has been stated that the centers 
of earthquakes have, with two exceptions, no greater depth than 
four to fourteen miles; therefore they are in no relation to that 
problematic region of general fusion. About 1871 many earth¬ 
quakes, were felt at the Comstock Lode, on one X3articular day 
twenty-four were counted. In the most cases they were not 
felt at all underground, and even then the shock was felt 
extremely feeble. It is seldom that shocks are felt under¬ 
ground in the collieries in Jax)an, where earthquakes are quite 
frequent. In many cases earthquakes and volcanic eruptions are 
different effects of a common cause. Earthquakes are also 
caused by the law of gravity coming into action by the 
undermining activity of the water; and when i^arts of the earth 
are so much contracted that the tension produced results in a ver¬ 
tical displacement of the rocks. Whenever a fissure was caused, 
the different rocks which suffered by it have undergone a physi¬ 
cal change according to their strength, hardness and cleavage. 
Hard crystalline rocks will be apt to wider and more irregular 
fissures, and appear more fractured and fragile in places where 
the fissure is smaller than where it is wide, because, during the 
dynamic proceedings the more i^rojecting parts of the walls had to 
suffer greater concussions. ' Thus we find in these narrow places 
in fissure veins, or where veins were filled with many rock frag¬ 
ments, that the wall-rocks are more impregnated with ore than in 
other places of the same veins, and we find more ore, because in 
consequence of shattering more surfaces were offered to the 
mineralizing waters which entered the fissure, and became at such 
places almost stagnant. 


22 


We know, from empyrical observations, that one and the same 
fissure-vein is very diiferent in regard to its ore contents, when it 
crosses different rocks. In such cases independent thinkers- 
among that old plutonic school—Breithaupt and Von Cotta, for 
instance—could not help to take refuge to the “lateral secretion’^ 
theory. But Professor Sandberger has given the scientific foun¬ 
dation for that theory, and when we evade the supposition that 
the minerali-zing process must have started in the crystalline rocks 
of the vicinity of the ore-deposit, as some rash critics have erro¬ 
neously done, his theory is most acceptable to explain the genesis 
of a good many ore-deposits in that state in which they are now. 
When, with the time necessary, the United States Geological Sur¬ 
vey will have more thoroughly completed their work, when, also,, 
outside of the Government work, the chemist and microscoi>ist 
will be called by mine owners, we shall know more about the pecu¬ 
liarities of our ore-dej)osits, and we shall then possess more of 
those clear descriptions of them, as Professor Sandberger has 
given us of the ore-deposits in some German mining districts in 
such a brilliant manner—of course, after a good many years of 
labor. 

It is remarliable that silicates as gangue are of rare occur¬ 
rence in all true fissure-veins, and, where they do exist, they are 
only of secondary origin. Fissure-veins carry free silica (quartz). 
But silicates are quite common in other deposits in districts where 
a Contact-metamori^hosis had taken place. I do not here speak of 
the silicates contained in the selvages nor of those contained in 
the fragments of the wall-rock mechanically mixed with the vein- 
material. This circumstance indicates that the process of ore-de¬ 
position in fissure-veins is going on under different physical con¬ 
ditions. 

The Ore-Deposits at Freiberg. 

37. Among the about one thousand fissure-veins at Freiberg cer¬ 
tain distinct periods are apparent to which they belong. All these 
fissure-veins occur in the rocks of the Archaean era, mostly in 
Gneiss. To the oldest formations of ore-deposits belong those 
filled with quartz and silver ores without Heavy Spar. Then those 
filled with quartz and sulphides of metals Then silver and lead 
ores with calcspar. The latest are filled with quartz, silver ores 
and Heavy Spar and fluor spar. The “Iron hat” of the veins con¬ 
sists of oxydes of iron and maganese. 




23 


The banded structure is more common in later formations, 
especially in the “Barytic Lead formation,” and the bands of the 
different spars were formed after the deposition of quartz and of 
the metallic sulphides; and wherever we find quartz or ore-bands 
• segregated subsequently to the spars, a new period of mineral 
formation is thereby indicated. In districts of so different vein- 
formations, we see just those veins to be the latest in origin, in 
which the spars predominate; they cross the other veins with pre¬ 
dominating quartz. Therefore, we may suppose that many dis¬ 
similar so called vein-formations are but formations of different 
leaching and precipitating periods. But in all this true fissure- 
veins, as they are shown in the text-books, rich and barren por¬ 
tions alternate irregularly. Von Cotta and the other Saxonian 
Geologists believe that the fissures of Freiberg and their filling 
out have to be considered as a consequence of the eruptions of the 
porphyries. 

38 A. The mines at Przibram, Bohemia, belong to the deepest 
in existence. Almost vertical Silurian slates carrying a remark¬ 
able amount of graphite are crossed by dykes of diabase and veins 
of silver, lead and copper ores. The veins are thick and rich, 
wherever they cross the slates; decrease in thickness and metals 
in a certain schist of clayslate, and pinch out when in contact with 
the diabase. The veins show a massive structure, seldom a banded 
one, and belong to those rare veins of argentiferous galena which 
improve in silver with depth. The diabase of Przibram is of a 
very old age. The vein-matter is mostly growm together with the 
wall-rock. 

Cripple Creek, Colorado. 

38 B. If we look from the top of Pike’s Peak, or from one of 
the prominent points between Pike’s Peak and Cheyenne Moun¬ 
tain in a southw^esterly direction, we notice between our standpoint 
and the Sawatch Range, a concentric declivity covered with num¬ 
erous small ridges of granite and eruptive rocks. This region is 
the Cripple Creek gold district of about thirty-six square miles 
with a diameter of almost seven miles. This region experienced 
three different periods of eruptions of rocks, the oldest of which 
seems to be the same which, at Leadville has been called Pyritifer- 
ous pophyry by the U. S. Chief Geologist Emmons. Its main fea¬ 
ture is the amount of pyrites which it contains. In later periods, 


24 


andesite and still later Rhyolite were emitted. The pyritiferous 
porphyry seems to occur only East and South of the town of Fre¬ 
mont, and it is just there where the most gold is found; not 
directly in this porphyry, but in fissure-veins of which we observe 
three different systems of fault-veins: Firstly, striking parallel* 
with the magnetic meridian of the district, for instance the cele¬ 
brated “Great View” mine; secondly, striking north-east and south¬ 
west, numerous dykes in this district run in this direction; thirdly, 
striking north-west and south-east, for instance, the celebrated 
Buena Vista Lode. 

Some of the veins have the character of “breccia,” the frag¬ 
ments of which have been cemented together by auriferous silica. 
But in all veins, without exception, we. observe that a general sili- 
fication process has taken place throughout this whole district. 
My idea about this process, mentioned in my paper read before 
the Chamber of Commerce at Colorado Springs last January, has 
been confirmed by Dr. Whitman Cross, of the U. S. Geological 
Survey, to whom I had sent specimens, and who wrote to me 
March 22d: “I think that all the quartz you see is secondary, 
filling the cavities of the breccia and, perhaps in some places, re¬ 
placing the rock itself.” 

Some of the veins occur in granite, some between granite and 
porphyry—for instance, the copperhead lode—but, presently, the 
best veins between the porphyries. Lithomarge often occurs in 
these veins, but never in great quantities, also opal (silica in 
amorphous state)—for instance, in the Pharmacist Lode. 

The detritus in this district contains no boulders, nor ce¬ 
mented gravel, while its gold seems to be in seams, instead of 
being more evenly distributed through the detritus. The source 
of the gold presently found in the veins of this district seems to 
have been in schists of the Archaean and Silurian periods. Along 
the lower Regua Gulch, the Wilson Gulch, the northern side of 
Grassy Gulch and the southern declivities of Tenderfoot and Min¬ 
eral Hills there is a granitic belt in the form of a horse-shoe, inside 
of which we find remnants of former schists of micaslate and 
other slates formerly overlying the Granite, also in place in the 
Sheriffs mine. In this granite belt we find along the eastern side 
of Wilson Gulch and along Mineral Hill auriferous quartz veins 
cropping out which MUST have been also in the formerly overlying 
schists, which, being friable, have been crushed and washed by 



25 


the waves of the former Silurian sea. Afterwards, when the por¬ 
phyries effected their eruptions and, still later, after the creation 
of fissures, the silification process went on and brought the 
gold in solution of sulphate of iron. On the road from Fremont 
•down to Squaw Gulch there is the round remnant of a former 
geyser, with its deposit of silica, and it stands on the line of a 
pyritiferous quartz vein. The conclusions to be drawn from this 
circumstance are easily left to the reader. 

39. The copper veins of Glarus, Switzerland, consist of a 
conglomerate of magnesian silicates and dolomite, crossing diassic 
sediments, in which they become richer in copper in proportion 
to the amount of fracture the sandstone has sustained. The solu¬ 
tions filled the veins to overflowing, impregnating the limestone 
and quartzite of that district, together with the conglomerate 
below them. Such a case of overflow is known also of veins in 
granite at Bourgogne, France, where the granite is overlaid with 
Jurassic arkose, the sediments of which are impregnated by ore 
and gangue of the same veins. 

40 A. In slateclay of the Cretaceous period at Bentheim, 
near the limits of Holland and Germany, there are several verti¬ 
cal veins of asphalt, crossing the slateclay at a right angle, show¬ 
ing within their thickness of three feet a symmetrically banded 
structure. On the two walls occurs a clayey asphalt, followed by a 
band of ironpyrites, then a band of calcspar, and the middle of 
the vein is filled with pure asphalt. 

40 B. Another example of asphalt veins is that in the Bitu¬ 
minous slate of the Carbonaceous period in New Brunswick, which 
rock is rich in fish-casts. This vein is from three to twenty feet 
in thickness. The books explain these veins as caused by oxyda- 
tion of the petroleum by the air. But, then, the asphalt must 
necessarily become hard at the top at first. Who would believe 
that air is able to penetrate such an impermeable material as 
asphalt, penetrate to such a depth? But the pyrites helps us to a 
better explanation. When^ under the influence of metamorphism, 
solutions of sulphates of iron and lime come in contact with petro¬ 
leum, pyrites is formed. In this case the petroleum lost a part of 
its hydrogen, forming sulphuretted hydrogen and water, while the 
oxygen in the suli^hates partly formed water and carbonic acid. 
•The calcspar bands in that vein tell us what became of the car¬ 
bonic acid and of the gypsum. 


/ 


26 


Wherever impervious covering of an oil-reservoir was wanting, 
a spontaneous decomposition must have taken place; the heavier 
parts sunk down, forming beds of asphalt. 

40 C. Similar veins of asphalt, containing about ninety per - 
cent of bitumen, exist in the Uncompahgre Ute reservation, a short 
distance from the Colorado State line. 

40 D. In the Cretaceous period, there were some rich silver 
ore deposits formed in the much-metamorphozed district of Irwin, 
Gunnison County, Colorado. Their particular genesis will be ex¬ 
plained by Mr. Emmons, of the U. S. Geological Survey. 

40 E. To the ore-deposits which occur in the Dominioii of 
the Cretaceous epoch, belong the cinnaber deposits near Borax 
Lake, Northwest from San Francisco; those of the Sulphur 
Springs in Calusa County, California, and those of the Steamboat 
Springs in Western Nevada, so well known by the fact that their 
formation is still going on, but not yet well known in regard to the 
sources from which they are derived. According to Professor 
Sandberger, they seem to be repeated depositions of ores con¬ 
tained in deeper-seated rock, and leached by the thermal springs. 

A good many ore-deposits certainly are of such secondary nature; 
in other words, they are products of different leaching and pre¬ 
cipitating periods. Lately, Mr. C. Kirkland has, in an interesting 
article in the Engineering and Mining Journal of New York, April 
13th, 1889, given a new example of two periods of mineralization 
and deposition in the Porcupine mine. Port Arthur, Ontario, 

Since volcanism has become a systematic study, we may infer 
that ore-deposits exist in deep-seated regions of eruptive rocks, 
from which, when the volcanic energy has declined, also metallic 
compounds were .leached by thermal springs and redeposited in 
higher horizons within the reach of mining; but after having 
been reformed out of deeper-seated deposits, they were still ex¬ 
posed to changes by leaching and redeposition in consequence of 
chemical action, and by the starting of percolating waters. There 
is no mining district in Colorado where this view will be better 
acknowledged after some years than in the San Juan region, com¬ 
prising the counties of Ouray, Hinsdale, San Juan, La Plata, San 
Miguel and Dolores. This region will be a great mining center of 
Colorado, when more railroads will be' built there, and when they 
will utilize their low grade ores by the help of pyrites, for the pro¬ 
duction of matte which will find a good market at the smelters in 


I 



27 


Denver and Pueblo. Some of the low grade ores of the San eJuan 
region may be successfully worked by mechanical concentration. 
The improved leaching process, as well as it works, will always be 
a precarious enterprise in these altitudes. 

Examples of Ore-deposits in their Third or Fourth Depo¬ 
sition; Ore-beds; Cave-deposits, Spring-deposits. 

41. In Nassau, Germany,. the Devonian dolomite was re¬ 
placed by deposits of maganese ore; that dolomite is rich in car- • 
bonaceous matter. 

42. At Iserlohn, Westfalia, Devonian Eifel limestone, rich in 
fossils, are overlaid with Tertiary clays and sand, derived from 
the volcanic rocks of the Eifel mountains. At their contact, and 
still in the limestone, the ore-deposits are found, in which zinc- 
blende takes the lowest place, while higher ui) the zinc occurs as 
carbonate and silicate. 

43. In the Traelures of the triassic .limestone at Wiesloch, 
Baden, the ore-dep o sits are the richest where sediments rich in 
fossils are in contact with the limestone. The fossils changed 
to zinc ore demonstrate the replacement of the limestone by the 
ore. 

44. Upon the ore-deposits within triassic limestones at Tarn- 
owitz, Silesia, the dolomite of the hanging wall has sometimes 
been entirely replaced by ores, leaving only its residues in a state 
of sand or clay. 

45. The cave-ores of the triassic limestone at Raibl in the 
Carinthian Alps are leaching products of the overlying marlslate 
rich in fossils, all of which have been changed to lithia-zincblende 
and galena; they have been carried down into the limestone caves, 
where they haiig as stalactites, or filled the cavities. 

46. In the ore-deposits in the Jurassic dolomites at Santan¬ 
der, Spain, the larger blocks of ore still show unaltered kernels of 
the dolomite. 

47. The globuliferous limonites found in caves within Juras¬ 
sic limestone in the Australian and Swiss Alps, in France, Baden, 
Bavaria and Wuertemberg, are mechanically produced cave-de¬ 
posits together with lignites, bones of Tertiary mammals and other 
fossils in clay and sand; but they also cover the bottoms of some 
valleys with a deposit one hundred feet in depth, proving them t6 
be deposits of mineral springs which had arrived at the atmos- 


28 


phere. In regard to their genesis, there must be some connections 
between them and their jurassic sediments of those extended dis¬ 
tricts, as the globuliferous limonites are not 'found in any other 
period. 

Examples of metallic deposits in Deteitus so common in 
Colorado, are not necessary in this review. Their genesis is found 
in the visible destructive activity of air and water in fluid and 
frozen forms. The statement that no sulphides and carbonates of 
metals occur in them, is not correct. Pyrites occurs in the Cali¬ 
fornia placers and in the detritus of the Cripple Creek district, 
Colorado. Carbonate of lead in the placers of the Mosquito Range, 
Colorado; native bismuth also is known in placers in French Gulch 
near Breckenridge, Colorado. Neither must there be a vein in 
the vicinity of a placer, nor is it true that platinum never is found 
in other deposits than in detritus; it occurs, for instance, together 
with nickel and cobalt in Canada. It seems that the auriferous 
eruptive rocks of the later periods are not so likely to form detri¬ 
tus as those of the ancient ones; the new gold district at Cripple 
Creek, Colorado, demonstrates that very well. 

From what source the metallic minerals contained in the cry¬ 
stalline rocks and in their derivatives had derived, is a problem. 
Rocks, thermal springs, the oceanic waters and volcanic emana¬ 
tions contain them. But as a source for industry, they are useful 
only where they have been concentrated by nature in the humid 
way. On a former page, an allusion has been made to that problem, 
to direct the attention of the readers to the researches of English 
Geologists, who, in more recent years, have attempted to help us 
to a better knowledge of volcanic action. I mention especially: 
“Volcanoes, by John W. Judd, 1881.” 

In the decline of volcanic energy, we observe the continuing- 
evolution of gaseous substances, the nature of which undergoes a 
regular series of changes In many mines we cannot miss evident 
proofs of former solfataric actions, which have prepared the work 
of the sequent thermal springs; nor do we miss series of changes 
in the filling of the veins. 

One of the consequences of the volcanic eruptions is the 
starting of thermal springs, which we meet so often in volcanic 
districts of every era. We may presume that in the depths of 
such springs the formation of ore-deposits is going on, although 
we cannot observe it so well as we do in some quicksilver deposits 


29 


in California. The gold deposit of the mine on Mount Morgan, 
Queensland, having paid a dividend of six million dollars in one 
year, had been deposited by a hot spring. 

The most ore-deposits are found in stratified rocks; this alone 
speaks for their genesis in the humid way. The entire mineral 
material of all stratified rocks has derived from the destruction 
and decomposition of former rocks, and is liable to be leached 
again. 

As the Archaeap period is the oldest geological period, its 
schists had to meet all these dynamic changes in our globe, and 
all the volcanic proceedings which have happened to this very day. 
Thus we find this period much richer in ore-deposits tljan any 
other period, especially in iron-ore. But the technical value of 
ore-deposits and their quantities are two different things. 

The best silver mines belong to the districts of rocks erupted 
during the Postcretaceous and Tertiary periods. The many ore- 
deposits in clayslates may have been the final consequence of 
earthquakes to which the clayslates are by their nature subjected. 
Of the immense number of ore-deposits discovered in the Altai 
Mountains, almost all their veins traverse sedimentary rocks of 
the Palaeozoic age, and are in visible connection with porphyries; 
several of them are worked in porphyry. 

Regions where accumulation of sediments was going on to 
gigantic measures, are characterized by considerable eruptions of 
rocks. For instance, the Appalachian chain was, according to Pro¬ 
fessor Dana, made up of sediments attaining a thickness of forty 
thousand feet, or eight miles; a part of the Rocky Mountains was, 
according to Clarence King, the former director of the U. S. Geo¬ 
logical Survey, built up of no less than sixty thousand feet, or 
twelve miles of strata. In the British Islands we observe fifty 
thousand feet, or ten miles of palaeozoic strata contorted by erup¬ 
tive rocks. 

Whoever had opportunity to see ore-deposits in various coun¬ 
tries must have been amazed at the change of the vein-materials 
when the same vein cuts rocks of different character; as much 
amazed as at the diversity of character exhibited by different sys¬ 
tems of fissure-veins which cut the same country rock. He will 
perceive how manifold the combinations of chemical and i3hysical 
circumstances had been in order to constitute an ore-deposit, al¬ 
though he conceives in each case that, instead of the ore-deposit. 


BO 


there was a water-way formerly. Thus we have to study the par¬ 
ticularities anew in each singular mining district. And it is left 
to the reader of this review to find out for himself why these 
examples of ore-deposits have been comi^iled in the order in which 
he finds them. 

The distances between the places where the processes of 
leaching, and then of precipitating were going on, may have 
often been great. The precipitating may have been done some¬ 
times by loss of pressure and corresponding loss of temperature, 
sometimes by carbonaceous substances or by reducing gases. As 
all the water percolating in our earth has been derived from the 
atmosphere, and as the scene of volcanic action has been continu¬ 
ally shifting to fresh areas at different periods of the earth’s his¬ 
tory, because accumulations of new sediments are going on, the 
observer will admit that the process of ore-building was not at¬ 
tributed to a certain age, but that it is still going on. He will 
understand that the mineral richness of Colorado and the other 
mining countries along the Kocky Mountains is not based on a 
greater primitive richness of these mountains, but on the fortu¬ 
nate circumstance thht, in consequence of great accumulations of 
sediments and of the resulting upheavals and destruction of for¬ 
merly superincumbent rocks, formerly deep-seated zones reached 
into our technical sphere, regions where the subterranean activity 
of force and matter has been alive for ages. 

Our public collections of minerals ought not to be mere col¬ 
lections of crystals; they ought to teach us their -paragenesis; 
only then they have a practical value, without which they are only 
tombstones of our scientific hod-carriers. As the paragenesis of 
the ores and gangue requires close observations, it is much neg¬ 
lected. Instead of the most necessary statements in reports on 
mines, we read profound sophisms about age and classification of 
the ore-deposits, and such verbal hocus-pocus is still allowed to be 
received as science, indicating the low state of knowledge in this 
branch, a feature of which we find in the history of every other 
science peculiar to its infancy. In studying ore-dei)osits we must, 
just as in any other branch of natural science, be anxious to point 
out facts for the progressive identification of ijhenomena, upon 
which the advance of knowledge depends. “ Many of the ques¬ 
tions of science remain unanswered, not by reason of the insuf¬ 
ficiency of our knowledge, but because the questions themselves 


81 


are founded on erroneous assumptions/ and require answers in 
irrational terms.” 


LITERATURE USED IN THIS REVIEW. 

1. Von Cotta’s Gangstudien and his Ore-Deposits. In these 
old books that galvanometric instrument is explained, which lately 
has been warmed uj) again as a new, wonderful thing. 

2. Baron Von Grodeck. Erzlagerstaetten. The author 
brings a good many examples of ore-deposits, but gets confused 
by establishing schoolmaster types, based upon mere mineralogical 
distinctions. The gradual replacement of rocks by ore-bodies 
the elements of which had been contained in the rocks was un¬ 
known to him. 

3. My Own Note-book, kept during my travels in Europe, 
Russia and America. 

4. Sandberger. Erzlagerstaetten. 

5. Judd. Volcanoes. 

6. Geology of Colorado Ore-deposits. By Professor A. 
Lakes, at the State School of Mines. Sometimes somewhat in¬ 
tricate, by terms inherited from the old plutonic school, which 
had prohibited explanations based on physics and chemistry. For 
instance, that handy theory of the old plutonic creed in violence, 
in regard to re-opening of fissures, reminds me of the musician 
who' accomplishes the necessary relief by opening one of the stops 
of his clarionet according to his pleasure. 

There was no such re-opening, but a decrease of volume of 
some gangue minerals; the empty space caused thereby has been 
filled afterwards again. For instance, when silica has been gradu¬ 
ally changed from its amorphous state into that of quartz, the 
decrease of volume amounts to 15.4 per cent. 

7. Having written this review while I was sick, I am very 
sorry that Professor Newberry’s book on ore-deposits was not at 
my disposition. Of course, like every other human work, it is not 
free of errors. For instance, Newberry speaks of the Humboldt, 
the Bassic and the Bull Domingo mines near Rosita and Silver 
Olitf, Colorado, “with ores as different as possible, while the three 
veins are contained in the same sheet of eruptive rock.” But the 
latter is not the case at all. According to the U. S. Geological 
Survey, the Bull Domingo deposit occurs in Archaean gneiss, while 
the Bassic and Humboldt bodies are in separate bodies of andesite. 






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